1. Field of the Invention
This invention relates generally to devices for sampling flowing fluids and, more particularly, to such devices which operate within a closed loop system.
2. Prior Art
In industrial chemical plants, as well as other industrial process operations, it is often necessary to obtain samples of fluids flowing in pipelines or various other types of vessels. Often, such fluids are of a hazardous nature, requiring that exposure of personnel to the sample be minimized or eliminated. In most applications where a sample is taken from a line flowing under pressure, samples are taken in sample cylinders. Such cylinders are well-known in the art. A typical cylinder is usually provided with a valve on either end, allowing a sample to be encased therein.
Various methods have been attempted in the art to safely force the sample into the cylinder. One method is to simply connect one end of the cylinder to the line containing the fluid, open the valve at the connected end and bleed the other end of the cylinder using the opposite valve until the cylinder is full of sample and entrained gases are displaced. This method obviously has its limitations with hazardous materials, since the bleeding step offers the possibility of exposing sampling personnel to the sample (a clear violation of current federal regulations). Other methods create a vacuum in the cylinder; elaborate means such as mercury or water displacement are also used. All of the prior art methods are prone to failure as well as exposure of sampling personnel to the sample. Further, these methods do not always result in a representative sample being contained in the cylinder or other sample container.
Stringent environmental regulations have resulted from an increasing concern over the safety of sampling personnel as well as exposure or discharge of hazardous materials to the atmosphere. Regulatory and safety concerns have thus severely limited sampling, resulting in elaborate and expensive containment schemes. Nevertheless, monitoring of industrial processes must still take place. The prior art devices have not managed to economically provide the necessary safety while maintaining the integrity of the sample.